This invention pertains to an inkjet ink comprising, as a binder additive, a polyazetidinium groups-containing compound, an ink set comprising this ink and a second co-reactive ink, and a method of printing with the ink and ink set. The co-reactive components of the ink set, when the inks are printed onto a substrate, chemically react to enhance the durability of the printed image.
Inkjet printing is a non-impact printing process in which droplets of ink are deposited on print media, such as paper, to form the desired image. The droplets are ejected from a printhead in response to electrical signals generated by a microprocessor. Inks used in such recording are subject to rigorous demands including, for example, good dispersion stability, ejection stability, and good fixation to media.
Inkjet printers offer low cost, high quality printing and have become a popular alternative to other types of printers such as laser printers. However, inkjet printers are presently unable to match the speed of laser printers and the durability of the laser printed images. Inkjet prints with increased durablilty would be highly advantageous.
U.S. Pat. No. 4,694,302 describes a two-pen configuration wherein one pen contains aluminium chloride in aqueous vehicle and the second pen contains a colored ink with carboxymethyl cellulose (CMC) in aqueous vehicle. When jetted together on a substrate, an insoluble salt of CMC is formed, producing a protective coating. The print was reported to be very waterfast.
U.S. Pat. No. 6,020,397 describes an inkjet printing process wherein a first liquid comprising aziridine and a second liquid comprising a polymer reactive with aziridine are sequentially applied to a substrate, thereby forming an aziridine-crosslinked polymer. Good ink adhesion was reported.
U.S. Pat. No. 6,503,307 describes a set of liquid compositions wherein a first liquid comprises a first water-soluble compound having an ethylenically unsaturated double bond with an alpha-electron withdrawing group, and a second liquid comprises a second water-soluble compound having an active hydrogen addable to the first compound. Colorant can be present in either liquid. When printed together on a substrate, the first and second liquids can react to form a polymeric film. Water and abrasion resistance are reported to be excellent.
US 2002/0156153 describes a two-part fixative comprising (1) a reactive monomer or oligomer, selected from the group of isocyanates and epoxy-terminated oligomers, in a vehicle and (2) at least one second component, selected from polyols and polyvinyl alcohols, and base catalyst. The reactive monomer or oligomer reacts with the second component on the print medium to form a polymer. Water-, smear- and smudge-fastness are reported to be enhanced.
US 2003/0087112 describes treating compositions for a variety of substrates, the treating compositions containing a functional component selected from an azetidinium polymer, a guanidine polymer, a mixture of the two polymers, and a copolymer of an azetidinium monomer and a guanidine monomer. The so-treated substrates are said to be useful as substrates in conventional and digital (inkjet) printing processes. U.S. Pat. No. 6,291,023 further describes the use of these treating compositions as coating compositions for textile substrates, while US 2003/0059636 further describes the use of these treating compositions as sizing compositions for paper substrates. There is, however, no disclosure of an ink composition based upon the functional components disclosed in the aforementioned publications.
The disclosures of all of the above-identified publications are incorporated by reference herein for all purposes as if fully set forth.
Still there is a need for inks and printing methods that provide more physically durable inkjet images.